I would love to be able to run a slideshow on a second screen based on a ‘live’ album in Aperture. So, when I drop an image into an Aperture album on my primary screen, it shows up when appropriate in the secondary screen slideshow.

I can live with having to take an explicit ‘publish changes’ type step from within Aperture, but I’d rather not, and I certainly don’t want the secondary slideshow to stop.